feat(infra): optimize AMD APU/iGPU lossless pipeline targeting H.265 cores

- Add detection for integrated AMD graphics (APUs/iGPUs) based on hardware model name
- Configure UMA-friendly full-range yuvj420p format to reduce system memory bandwidth footprint by 50%
- Force lossless constant QP (-qp 0) and full PC range to prevent clamping loss
- Re-run syntax checks and Lean compiler verification tests

Build: 3313 jobs, 0 errors (lake build)

4-Infrastructure/shim/vcn_compute_substrate.py

@@ -272,8 +272,21 @@ def load_math_optimizations(vendor: str, gpu_name: str) -> MathOptimizationLoad:
 
     # 2. AMD Radeon / Ryzen APU with VCN (Video Core Next)
     elif vendor == "amd":
-        # AMD VCN supports VAAPI or AMF
-        # H.265 lossless constant QP
+        # Check if it is an integrated GPU / APU (shared system memory)
+        is_igpu = "graphics" in gpu_name or "integrated" in gpu_name or "apu" in gpu_name or "drm" in gpu_name
+
+        if is_igpu:
+            # iGPU/APU: Optimize for memory bandwidth limits of unified system RAM
+            opt.pixel_format = "yuvj420p"  # Full-range YUV420 (saves 50% system RAM bandwidth over YUV444)
+            opt.bit_depth = 8
+            opt.packing_density = "independent_y_6x" # Independent Y-plane utilization
+            opt.color_range = "pc"         # PC range (0-255) to prevent clamping loss
+            opt.encoder_opts = [
+                "-qp", "0",                # VAAPI / AMF Lossless QP
+                "-color_range", "pc"
+            ]
+        else:
+            # dGPU: High dedicated VRAM bandwidth, use YUV444p for maximum packing density
             opt.pixel_format = "yuv444p"
             opt.bit_depth = 8
             opt.packing_density = "yuv444_3x"
@@ -283,6 +296,7 @@ def load_math_optimizations(vendor: str, gpu_name: str) -> MathOptimizationLoad:
                 "-color_range", "pc"
             ]
 
+
     # 3. Intel Graphics
     elif vendor == "intel":
         opt.pixel_format = "yuv422p"